Abstract: Prophenoloxidase (PPO) is a key enzyme of insect immunity. In this study, the nucleotide sequence and deduced amino acid sequence of PPO cloned from the larvae of Ostrinia furnacalis were analyzed and predicted by the tools of bioinformatics in the following aspects: the composition of nucleotide sequences and amino acid sequences, signal peptide, trans-membrane topological structure, hydrophobicity or hydrophilicity, secondary structure, tertiary structure, etc. The results showed that the full-length cDNA of O. furnacalis PPO (Of-PPO) consisted of 2 686 bp, containing an open reading frame (ORF) of 2 079 bp. Based on the 693 deduced amino acid sequences of Of-PPO, a putative thiolester site and two distinct copper binding regions were found, which included six histidine residues. Of-PPO belongs to the PPO2 group, and there is no signal peptide in the N-terminal region of the polypeptide chain. No possible transmembrane protein model was found. There was no O-glycosylation site in Of-PPO predicted with DictyoGlyc. Forty-four phosphorylation sites were predicted in the whole peptide by NetPhos 2.0 Server. Two regions of Of-PPO could form coil structures, and five regions were found with significant hydrophobic characteristics. The proportions of α-helix and random coil in the secondary structure of Of-PPO were 22.54% and 56.79%, respectively. The comparative modeling method was used to calculate the tertiary structure of Of-PPO, and the result showed that it was the “roller” shape, which belongs to the α/β type. The catalytic activity may relate with a large vacant space in Of-PPO structure analyzed by the RasMol software. This study may provide valuable information for further research on Of-PPO.

Key words: Ostrinia furnacalis, prophenoloxidase, bioinformatical analysis, tertiary structure, comparative modeling